I. Field
The following relates generally to wireless communication, and more specifically to preamble design of a wireless signal facilitating reduced interference for semi-planned or unplanned wireless access networks.
II. Background
Wireless communication systems are widely deployed to provide various types of communication content such as, e.g., voice content, data content, and so on. Typical wireless communication systems can be multiple-access systems capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power). Examples of such multiple-access systems can include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and the like.
Generally, wireless multiple-access communication systems can simultaneously support communication for multiple mobile devices. Each mobile device can communicate with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from base stations to mobile devices, and the reverse link (or uplink) refers to the communication link from mobile devices to base stations. Further, communications between mobile devices and base stations can be established via single-input single-output (SISO) systems, multiple-input single-output (MISO) systems, multiple-input multiple-output (MIMO) systems, and so forth.
Wireless messages are typically sub-divided in time, frequency, according to codes, and so on, to convey information. For instance, in an ultra mobile broadband (UMB) system, forward link messages comprise at least one time superframe (e.g., of 25 millisecond length) segmented into one superframe preamble and several time frames. The preamble carries acquisition and control information, while the various other time frames carry traffic, such as voice information pertinent to a voice call, data packets pertinent to a data call or data session, or the like. Acquisition information can be utilized by mobile terminals within a given mobile network sector to identify transmitting base stations within the sector. Control channel information provides commands and other instructions for decoding received signals.
In UMB, a superframe preamble comprises eight orthogonal frequency division multiplex (OFDM) symbols. The first symbol typically carries a forward primary broadcast control channel (F-PBCCH) and the next four symbols can carry a forward secondary broadcast control channel (F-SBCCH) and forward quick paging channel (P-QPCH). The F-PBCCH and F-SBCCH typically provide initial configuration information required by terminals entering a UMB system. For instance, the F-PBCCH channel might carry deployment-wide configuration information that is common across sectors, while the F-SBCCH might carry sector-specific configuration information. The F-QPCH can carry quick pages which are used to direct idle mode terminals to read a page and open a connection if a page is received.
The last three OFDM symbols of the UMB preamble can carry acquisition pilot information. The first of these three symbols typically carries a sector-independent signal used to determine the existence of a UMB system and to acquire initial timing and frequency. A second, sector-dependent signal can be utilized to determine identity of a transmitting sector and/or base station. A third signal, also sector-dependent, can carry information used to determine initial system parameters such as whether the system is synchronous or asynchronous, what time division duplex (TDD) partition to use, and so on. In another example, for instance with a third generation partnership project long term evolution (3GPP-LTE) network, acquisition pilot information can comprise different signals than those specified above for the UMB example. For instance, the 3GPP-LTE system typically employs a primary synchronization code (PSC), secondary synchronization code (SSC), and a packet broadcast channel (PBCH) as acquisition pilot signals. Although the synchronization signals can comprise different forms (e.g., sequence lengths, scrambling sequences, modulation and timing, etc.), similar information can be conveyed by these signals. Thus, for instance, LTE codes can convey identity of a transmitting sector/base station, timing and modulation information for decoding received signals, default system parameters, and the like. The LTE codes can be conveyed utilizing a portion of the OFDM symbols of an LTE preamble (e.g. localized in time and in frequency) as is known in the art.
While the foregoing describes a preamble for UMB and LTE systems, various other mobile communication systems also utilize channel preambles, or similar structures, for signaling, acquisition, control or like wireless communication functions. Other functions can include specifying formats of traffic channels for some wireless systems. Typically, a preamble is set apart from a traffic-related portion of a wireless signal to facilitate distinction of application-related information and control information at a receiver. Thus, the receiver can monitor control portions to identify whether a signal contains traffic pertinent to a receiving device, without having to monitor the traffic portions themselves. Because the control portion is typically only a small fraction of the total signal, receiver devices can significantly reduce processing requirements and power consumption by monitoring a signal preamble to determine whether relevant information is contained in the signal. Employing control channels for wireless signaling therefore leads to more effective communication, as well as improved mobility by extending battery life for mobile devices.